Field of the Invention
The present invention relates to a method of protecting redundant servers coupled to a manufacturing executing system (MES).
A method for managing and controlling manufacturing and/or analysis processes planned by an enterprise resource planning (ERP) and produced by a technical process line, provides in the environment of a manufacturing executing system (MES) an automation (or batch) system for implementing the planned analysis processes and controlling the corresponding workflow steps at the level of the technical process line.
In particular, the enterprise resource planning (ERP) is a system including hardware devices and corresponding software applications for planning the business resources of an enterprise, i.e. material provisions, human resource managements, purchasing, orders, profits, finance, inventory controls, customer managements, etc., while the term “technical process line” refers to a system supporting the control of single machines involved in the analysis processes, for example by measuring the number of pieces handled per hour by each machine or the functioning parameters thereof, the quality of the analysis results and so on.
MES is an intermediate layer providing computing machines and software tools between the ERP upper layer and the process line lower layer, including a software tool for analysis management, which receives requests of analysis from the ERP, and a software tool for productive process, which supports the phases of selecting and managing the resources to be involved in the productive processes, i.e. employees, machines and materials, in order to realize a planned analysis process within required time constraints.
MES is based on the International Standard Association (ISA) standard S95 which defines how software tools may implement the productive process at a plant floor level and how to communicate with it. Beside the productive process itself, it is crucial for many industries to control the productive process in terms of analysis, measurements and traceability of the products, like for example for pharmaceutical industry, food industry, high-tech industry, or for industries where the productive process itself is a process of analyzing a sample, i.e. medical diagnostic analysis, material science analysis, drug scanning and so on.
A batch system is an automation system part of the lower layer. A batch system provides computing machines and software tools to drive and monitor pieces of equipment at the plant floor level. A batch system contains a set of basic recipes, which defines steps for driving a piece of equipment in order to realize a given basic task. In other words, the batch system controls actuators—like so called programmable logic controller (PLC) units of a piece of equipment in order to perform a given task at the plant floor level.
FIG. 1 presents a schematic overview of an interface between a MES and a batch system PLC containing a plurality of PLC units. Sequentially the MES is coupled to at least two redundant process servers PI1, PI2, the process servers being coupled with at least two redundant servers EPE1, EPE2 (=as Element Procedural Elements servers), the servers EPE1, EPE2 acting as main and shadow interfaces between respectively the at least two redundant process servers PI1, PI2 and at least two redundant control servers OPC1, OPC2 (as Operational Process Control OPC-servers according to known OLE-technology: the OPC Specification was based on the OLE, COM, and DCOM technologies developed by Microsoft® for the Microsoft Windows® operating system family. The specification defined a standard set of objects, interfaces and methods for use in process control and manufacturing automation applications to facilitate interoperability, the servers OPC1, OPC2 being coupled to an automation part containing the batch system PLC with its controllers 1, 2, 3. In other words the interface between the MES and the batch system PLC contains hence at least two redundant data paths in case one of the servers would be defect. In the example of FIG. 1 it is assumed that the path PI1, EPE1, OPC1 is considered as a main path and the other path PI2, EPE2, OPC2 as a shadow path. Principally both main and shadow path transmit the same information between the MES and the batch system PLC. In case e.g. the server EPE1 in the main path is defect, the server EPE2 in the redundant shadow path will take over the lead of the transmission to guaranty the protection of the transmission. Other crossed protection paths (see vertical and oblique arrows) between servers of each one of the main and shadow (horizontal) paths are also possible in order to permanently ensure at least one secure transmission between the MES and the batch system PLC.
Such a management of redundancy of servers is however impacted with long time delay due to a detection of failure by one server. In other words at the side of the batch system the productivity of the plant floor will be slower by such a detection which is principally based on also varying values of automation data.
There is therefore a need to improve—in terms of time and robustness—the detection of failure of servers for a system as presented in FIG. 1, especially if one of the at least two redundant servers EPE1, EPE2 (Element Procedural Elements servers) fails.